I was able to repro this with Trieuii earlier. We saw it most frequent with server changes but there were other instances where if the game crashed(assuming its crash because you get black screen) you could not reconnect to the server you were in before the crash.
Repro Steps :
Connect to a sever
Once in game change severs.
On changing servers if you get a long black screen restart the application
Log in and try and join a server. Note you will see the temporary ban on joining other servers.
You will not be able to stay connected to the available server
Your guild mates can see you sign on, and disconnect. Message for the user is Disconnected please try again.